1. Field of the Invention
The present invention relates generally to a prefilled injection device for delivering a dose of medicament by injection and having a sealing system for preventing contamination of the injection device prior to its usage. More particularly, the present invention is directed to a syringe assembly including a sealed luer fitting.
2. Description of the Related Art
Syringes used for the delivery of medicaments to patients are well known. Oftentimes syringes are prefilled with a dosage of a medicament or other substance by a pharmaceutical manufacturer and then distributed to end users such as health care professionals or patients for administration of the prefilled dosage of medicament.
A “compression syringe” used herein refers to a syringe which holds medicament in a reservoir defined by walls with at least one being compressible when squeezed by a user's hand. Compression syringes can be prefilled with a single dose of the medicament, which can be expelled out from the reservoir upon compressing the reservoir. Because of their lightweight and compact properties, their ruggedness and low cost, compression syringes are widely used in many circumstances.
U.S. Pat. No. 4,955,871 discloses a compression syringe 10; the entire content of the U.S. patent is hereby incorporated by reference. As is depicted in FIGS. 1 to 3, a conventional compression syringe 10 has a needle assembly for injecting the medicament into the patient. The needle assembly includes a needle cannula 12 passing through and fastened in a needle hub 20. The needle assembly also includes a nozzle 18 having a closed end connected to an injection port and an open end for holding the needle hub 20. The closed end of the nozzle 18 is formed by a nozzle membrane 22.
The needle cannula 12 of the needle assembly is pointed at both sharp pointed end 14 and tip 16. The sharp pointed end 14 can penetrate nozzle membrane 22 when needle hub 20 is moved toward the nozzle membrane 22. The tip 16 of needle cannula 12 is used to administer the medicament, for example intravenously, or intramuscularly through the skin of a patient.
The needle hub 20 of the needle assembly is made of polystyrene and is preferably secured to needle cannula 12 using an adhesive, such as an epoxy resin. The needle hub 20 can be cylindrical in shape and have a first section 24 of large diameter and a second section 26 of small diameter. The dimensions of large diameter first section 24 and of the internal diameter of a cylindrical nozzle 18 are selected so that needle hub 20 is frictionally held within the cylindrical nozzle 18, but can be moved laterally within the nozzle 18 when a force is applied to needle hub 20, as explained below.
The nozzle 18 of the needle assembly can be cylindrical in shape. An internal rib 28 is formed between nozzle membrane 22 and needle hub 20 to prevent sharp pointed end 14 of the needle cannula 12 from piercing the closed end of the tube unless a sufficient force is applied. The dimensions of internal rib 28 and of large diameter first section 24 are selected so that needle hub 20 will not move past rib 28 unless a sufficient force is applied to needle hub 20. This structure reduces the risk of unintentional piercing of nozzle membrane 22.
The compression syringe 10 has a protector cap 30, which cooperates with the nozzle 18 to enclose and protect the needle cannula 12. The open end 34 of the protector cap 30 is configured to fit inside the nozzle 18 and preferably has an external diameter so selected to be snugly held in position within the nozzle 18. The protector cap 30 is long enough to prevent its closed end 32 from contacting the tip 16 of the needle cannula 12 when the needle cannula 12 is enclosed in the protector cap 30 and the nozzle 18. As a result, the protector cap 30 and the nozzle 18 keep the needle cannula 12 sterile during storage and shipment of the compression syringe 10.
The protector cap 30 and the needle hub 20 cooperate with each other to axially move the needle cannula 12 within the nozzle 18. The internal diameter of open end 34 of the protector cap 30 is selected so that the small diameter second section 26 of needle hub 20 fits snugly within the open end 34 of the protector cap 30. The external diameter of open end 34 of the protector cap 30 is selected so that the protector cap 30 can be moved laterally within the nozzle 18. The protector cap 30 so formed can be used as a tool in which the open end 34 of the protector cap 30 is pushed against the large diameter first section 24 of the needle hub 20. In this way, a sufficient force can be safely applied to the needle hub 20 to force it past internal rib 28. The protector cap 30 then continues pushing large diameter first section 24 of needle hub 20 until sharp pointed end 14 of needle cannula 12 pierces the nozzle membrane 22.
The compression syringe 10 also includes a reservoir 46 for storing medicament and for expelling the medicament into the needle assembly. The reservoir 46 is formed from a pair of flexible sheets 38a and 38b of thermoplastic material. Each sheet 38a, 38b has a central portion 40, an expanded injection neck portion 42, and a substantially flat peripheral portion 44. The peripheral portions 44 of the two sheets 38a, 38b are opposite and coextensive to each other and are sealed together face-to-face to form a reservoir 46. The reservoir 46 can be filled with medicament via a filling neck portion 56 (see FIG. 1) having a filling port 58 as explained more fully in U.S. Pat. No. 4,955,871. Following the filling step, the filling neck portion 56 of the two flexible sheets 38a, 38b are heated sealed together by a sealing portion or region 57 (see FIG. 2).
To activate the compression syringe 10 of FIGS. 1 to 3, the protector cap 30 is pushed back towards the needle hub 20 to cause sharp pointed end 14 of the needle cannula 12 to pierce the nozzle membrane 22, thus placing the needle cannula 12 in fluid communication with the reservoir 46. The protector cap 30 is then removed to expose the tip 16 of the needle cannula 12 for administering an injection to a patient. To administer the medicament, the central portion 40, i.e., the flexible wall of the reservoir 46, is compressed, such as between the thumb and forefinger of the user. After the medicament is administered, the needle cannula 12 is withdrawn from the patient and covered to avoid exposure and possible contamination from the used needle tip 16.
The above described compression syringe 10 is however incompatible with a luer connector and unable to administer the medicament through a luer connector.
FIGS. 4 and 5 show another conventional luer-type syringe 10′, which employs a luer fitting 19 to deliver medicament directly to a luer connector. Luer-type syringes 10′ are typically sealed by a cap 31, which can be twisted-off to expose the luer channel 21 at the luer tip. Such cap 31 however can be accidentally damaged or removed during shipping or handling of the luer-type syringes 10′ causing such syringes 10′ unfit for their normal use. In addition, as the luer fitting 19 is intended to be directly fit in a sterile luer connector the luer fitting 19 or the entire syringe 10′ must be sealed to protect the luer fitting 19 from contamination prior to the use of the syringe 10′.
These and other disadvantages can adversely affect the operation of such luer-type syringes 10.
Accordingly, there is need for an injection device with a luer fitting so as to be directly insertable into a compatible female luer connector for administering medicament therethrough. In particular, there is need for an injection device with a protected luer fitting that is shielded from contamination during the handling of the injection device.
The embodiments below describe an injection device that is sealed against leakage through its luer tip of content from the medicament reservoir. Additionally or alternatively, the male luer fitting of the injection device is sealed from outside contamination prior to the use of the injection device.